A study in the latest issue of The Journal of Law and Economics finds a link between out-of-wedlock births and rates of murder and other crimes.

According to the study, in the years from 1965 to 2002, higher rates of out-of-wedlock births in a given year correlate with higher crime rates roughly 20 years later, when members of that birth cohort had become adults. The findings suggest that children born out of wedlock may receive lower educational and other resource investments from their parents, and may therefore be more likely to commit crimes as adults, say the study’s authors, economists Todd D. Kendall, of the consulting firm Compass Lexecon, and Robert Tamura of Clemson University.

“While a number of previous studies have found that unmarried fertility is associated with unfavorable childhood outcomes, our analysis is one of the first to measure the long-run effect on crime when these children reach adulthood,” Kendall and Tamura write.

According to the analysis, an increase of 10 out-of-wedlock births per 1,000 live births was associated with up to a 5 percent increase in future murder rates. The researchers find that most of the large increase in the number of murders in the U.S. during the 1970s and 1980s can be explained by out-of-wedlock births.

The study used crime statistics and birth records from 1923 to 2002 in the 32 U.S. states that record the marital status of parents.

ROLE OF SOCIAL STIGMA

While Kendall and Tamura found that more out-of-wedlock births are associated with higher subsequent crime rates over the last 45 years, they found just the opposite for years prior to 1965. In the 1940s and 1950s, small increases out-of-wedlock births actually correlated to lower subsequent murder rates.

Why did the association change? Kendall and Tamura argue that changing social attitudes toward unwed motherhood are the primary reason. In the 1940s and 1950s, social stigma against unwed mothers was intense, and as a result most pregnant couples ended up getting married—even couples who were very poorly matched. Some of those marriages would have been so bad that the children involved might have been better off—and less inclined to commit crimes as adults—if their parents had never married. So a moderate increase in out-of-wedlock births during this period meant that fewer poorly matched couples were forced to marry, thus exposing fewer children to damaging marriages.

In the 1960s and 1970s, however, social attitudes toward unwed motherhood changed rapidly and rates of out-of-wedlock births skyrocketed. Many of the marriages foregone during this period would have been relatively well-matched couples, Kendall and Tamura argue. “The children of these higher-quality matches are worse off because of their parents’ failure to marry, and have higher risks of adult criminality,” they write.

ABORTION AND CRIME

In 2001, economists John Donohue and Freakonomics author Steven Levitt published a controversial paper linking lower crime rates in the 1990s with the legalization of abortion 20 years earlier. Donohue and Levitt contend that abortion lowered crime rates because many children who would have become criminals as adults were never born. Some commentators pilloried the study as implying that society benefits from abortion.

Kendall and Tamura’s study supports the idea that abortion does reduce future crime, but shows that the primary cause of this effect is the reduction in children born to unmarried parents. “Our findings suggest that promoting marriage among new parents could be as effective in reducing crime as loosening abortion restrictions,” Kendall said. “We show that abortion is a blunt policy lever for affecting crime rates.”